For whatever reasons, occasions arise when I have to remove the spark plug cap (a while ago I changed the spark plug, recently I just rebuilt my engine, and some other time I decided to check the tightness of the spark plug, whatever).

So I don't purposely take the spring off. What I was trying to say is that when I take off the spark plug cap, that's when the spring falls out and I never notice until I see it laying on the floor after I've already put my cowl back on. It's not a big deal, just a bit of a hassle (because, to remove the spark plug cap to put the spring back in, I remove my cowl (and spinner and propeller) so I don't tear it up - I have my cowl cut pretty close to the spark plug cap and wire).